Electricity from Biomass

The cheapest, most used, and simplest way of using biomass to generate energy is to burn it. On a commercial scale, this is done in a process similar to the one burning coal to produce electricity or heat. In these applications, wood, wood waste and municipal solid waste are the most utilized fuels. The average plant has generally a small size (around 20 MW) and an efficiency ranging from 15 to 30% for conversion to electricity [5]. With co-generation of electricity and heat, the total efficiency can reach 60%. Methane-rich biogas, if captured and collected from landfills, can also be used to generate sizeable amounts of energy.

New technologies that are commercially available for converting biomass to electricity include co-firing and gasification. Co-firing power plants use biomass as a supplementary energy source with a conventional fuel, typically coal. Gasification converts solid biomass through partial oxidation at high temperature into a combustible gas, containing mainly carbon monoxide and hydrogen. The gas produced can then by burned in a gas turbine or internal combustion engine to generate electricity. It is worthwhile noting that during the great depression and World War II, small gasifiers were used for cars to convert wood and charcoal

Table 8.1 Production of electricity from biomass and waste in 2003.

Country

Production (TWh)

Percentage of world electricty production from biomass

Percentage in the country's total electricty production

United States

64.6

32.4

1.7

Japan

25.9

13

2.5

Germany

12.3

6.2

2.2

Finland

10.6

5.3

12.6

Brazil

10.4

5.3

3.2

Canada

8.3

4.1

1.6

United Kingdom

6.2

3.1

1.7

Spain

5.5

2.8

2.4

Rest of the world

55.4

27.8

0.7

World

199.1

100

1.4

Data source: EDF and IEA key statistics.

Data source: EDF and IEA key statistics.

to gas that was fed to the engine. These vehicles were not very efficient and needed extensive maintenance, but nevertheless functioned quite well.

The cost of biomass energy varies widely depending on the fuel, its quality, and the technology used. Electricity-generating costs are however generally higher than those for fossil-fueled plants because of lower efficiencies, higher capital, and fuel costs. Most estimates for the fuel cost are in a range of $150 to $250 per tonne, but this can be much lower in cases where the fuel is a byproduct from some other process [5].

Among the OECD countries (Organization for Economic Co-operation and Development, including most developed nations), electricity from bioenergy represented 1.6% of the total electricity generation in 1999 [5]. More than half was produced from solid products such as wood and agricultural residues, while waste accounted for 35% of electricity produced by biomass. In 2003, in forest-rich Finland, electricity from bioenergy represented 12.6% of the total electricity production, but only 1.7% in the United States (which has overall the largest electricity generation capacity from biomass, but also the highest electricity consumption).

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